Reliable and effective techniques for removing contaminants from soil are highly desirable. However, metolachlor residue bioremediation and soil fertility improvement by Rhodospirillum rubrum (R. rubrum) in effluent after wastewater treatment have not yet been investigated. The aims of this study were to investigate the feasibility of bioremediation of metolachlor residues in soil and soil fertility improvement by R. rubrum in effluent and to explain the mechanism that R. rubrum in effluent was induced to express the regulatory gene.
Materials and methods
Soybean processing wastewater was obtained from Harbin Soybean Products Machining Factory. Soil samples were the surface soil (0–30 cm) from campus (1.77 g/kg total N, 4.15 g/kg total P, 1.58 g/kg total K, 17 g/kg SOM, 0.07 g/kg SMBC). Cytochrome P450 monooxygenase regulatory gene, MAPKKKs gene, was measured by RT-PCR.
Results and discussion
Compared to control treatment, metolachlor was removed efficiently and soil fertility was remediated by effluent containing R. rubrum. The removal in concentrations reached 2.97 mg/L (99%). Soil organic matter (SOM) and SMBC were enhanced 42 times. Molecular analysis revealed that metolachlor induced cpm gene expression to synthesize cytochrome P450 monooxygenase through activating MAPKKKs gene in MAPK signal transduction pathway.
Conclusions
Bioremediation of metolachlor in soil and improvement of soil fertility using R. rubrum in effluent were feasible. Metolachlor, as environmental pressure, induced cpm gene expression to synthesize cytochrome P450 monooxygenase and to remove metolachlor through activating MAPKKKs, MAPKKs, MAPKs genes in MAPK signal transduction pathway.
In solution culture at different iron (Fe) concentrations, both contents of endogenous hormones or the IAA oxidase activities in the roots and the diffusive IAA contents in the stem apex were analyzed for Malus xiaojinensis (an Fe-efficient apple genotype) or M. baccata (an Fe-inefficient apple genotype). The results showed that higher amounts of IAA in M. xiaojinensis were transported from the stem apex into roots under Fe deficiency stress, which resulted in a great enhancement of the root IAA content, being 4–5 times higher at Fe deficiency than at a normal Fe level. Root IAA content of M. baccata did not show any obvious change at both deficiency and normal level of Fe. When the appearance of leaf chlorosis was used as the test point by the time, there was no remarked difference in fluctuation of the root GA3 or ABA contents between M. xiaojinensis and M. baccata, although the developing trends of the root GA3 or ABA contents were slightly lagging for M. xiaojinensis. The results obtained in this experiment suggested that IAA might be a signal factor of inducing Fe deficiency response in plant of genus Malus. 相似文献
Four‐year‐old ‘Aki Fuji’ apple trees in their second leaf of fruiting were used to study the influence of paclobutrazol on photosynthesis rate (Pn) and the partitioning of dry matter in the different parts of the tree. It was found that the Pn of paclobutrazol‐treated trees was significantly higher than the untreated check trees. This is partially accounted for by the higher light intensity in the canopy of the paclobutrazol‐treated trees. Production efficiency of the paclobutrazol‐treated trees was 2.6 times higher than that of the untreated check trees. Paclobutrazol significantly changed the partitioning pattern of dry matter in the different parts of the tree. A much higher percentage of total dry matter was distributed to the fruit. However, a higher percentage of dry matter was found in the root of the paclobutrazol‐treated trees than in the untreated trees, the difference being mainly in the lateral and fibrous roots. Total dry matter accumulated per m2 of occupied land of the paclobutrazol‐treated tree was 4% greater than that of the untreated check trees, whereas total dry matter accumulated per kg of leaves was essentially the same in both trees. Whether calculated on the basis of per m2 of occupied land or per kg of leaves, the dry matter distributed into the fruit and into the root was considerably greater in the paclobutrazol‐treated trees than the untreated trees. 相似文献
Abstract The issue of soil organic carbon (SOC) is of increasing concern. Because SOC, as an important soil component in farming systems, is essential for improving soil quality, sustaining food production and quality, and maintaining water quality and as a major part of the terrestrial carbon reservoir, it plays an important role in the global carbon cycle. In this paper, a total of 665 soil samples from different depths were collected randomly in the autumn of 2007, and the spatial variability of SOC content at a small catchment of the Loess Plateau was analysed using classical statistics and geo-statistical analysis. In nonsampled areas classical kriging was utilized for interpolation of SOC estimation. The classic statistical analysis revealed moderate spatial variability with all five layers of SOC-content. In addition, the average SOC content decreased with soil depth and the relationship can be modelled by an exponential equation (y=3.1795x?1.2015, R2=0.9866) and all of the SOC-content data in the different depth were normally distributed. The geo-statistical analysis indicated a moderate spatial dependence in 0–60 cm, while in the 60–80 cm depth spatial dependence was strong. The semi-variogram could be fitted by an exponential model for 0–10 cm depth; by a spherical model for 10–20 cm depth and 60–80 cm depth; and by a Gaussian model for 20–60 cm depth. The range increases with increasing depth. In addition, classical kriging could successfully interpolate SOC content in the catchment. In general, the geo-statistics method on a watershed scale could be accurately used to evaluate spatial variability of the SOC content in the Loess Plateau, China. 相似文献
Solution culture with four pH levels was employed in this experiment to evaluate root and rhizosphere responses of Malus xiaojinensis [iron (Fe)‐efficient species] and M. baccata (Fe‐inefficient species) in order to pursue some of their physiological mechanism for Fe absorption. The results showed that M. xiaojinensis had a higher fresh weight per seedling than M. baccata at any of the solution pH levels tested and the differences were significant between the two species with increasing of the solution pH levels, particularly at the pH of 7.4 or 8.4. The reducing abilities of root exudates for the two species under test were decreased with increasing of the solution pH from 5.4 to 8.4, in which the reducing abilities for M. xiaojinensis were always more than two times higher than those for M baccata. The significant decrease of the reducing ability was found only at pH of 8.4 for M. xiaojinensis or at both 7.4 and 8.4 for M. baccata, respectively. Malus xiaojinensis had significantly higher respiration rates than M. baccata at the higher solution pH levels. Both rhizosphere pH and rhizosphere redox potential were influenced by the solution pH levels remarkably in distances of 0–4 mm to root surface or in distances of 5–10 mm along the root from the root tip, respectively. Genotypic differences in these two parameters were clearly showed at the solution pH of 7.4, in which rhizosphere pH of M xiaojinensis was clearly lower than that of M. baccata, while the rhizosphere redox potential of the former was much higher than that of the latter. 相似文献